The present invention relates to a technique effective when applied to an electronic part having a high frequency power amplifier circuit assembled therein, used for a radio communication system such as a mobile cellular phone and for amplifying a high frequency transmission signal and outputting the amplified signal, and more particularly, to a technique effective when used for a circuit for detecting output power necessary for an output power feedback control.
Generally, in a transmission-side output part in a radio communication system (mobile communication system) such as a mobile cellular phone, a high frequency power amplifier circuit for amplifying a modulated transmission signal is provided. In a conventional radio communication system, to control the amplification factor of the high frequency power amplifier circuit in accordance with a transmission request level from a control circuit such as a baseband circuit or a microprocessor, the output power of the high frequency power amplifier circuit or an antenna is detected and fed back (refer to, for example, Japanese Unexamined Patent Publication No. 2000-151310). Hitherto, the output power is generally detected by using a coupler, a detector, or the like. The detector is often constructed in a semiconductor integrated circuit separate from the high frequency power amplifier circuit or as a discrete part.